The subject matter disclosed herein relates to a flush valve structure for a toilet tank.
FIG. 4 of copending U.S. patent application Ser. No. 11/775,433 discloses a single volume flush valve structure for a toilet tank. The single volume flush valve structure comprises a valve base that is secured in the outflow hole of the toilet tank. An extension flares upward from the valve base and a first part of a valve seal is attached to, or integrally formed with, the extension at the upper end thereof. A vertical guide is attached to the valve base and extends upward therefrom and a float assembly is fitted slidably over the guide. The float assembly includes a second, complementary, part of the valve seal, which engages the first part of the valve seal when the float assembly is in a lower position relative to the valve base. Because of the flared nature of the extension, the float assembly is typically of somewhat greater diameter than the outlet hole of the toilet tank. A pressure difference across the seal holds the two parts of the seal in sealing relationship. When the float assembly is lifted relative to the valve base, water passes between the two parts of the valve seal and relieves the pressure difference that would otherwise exist across the seal, allowing the float assembly to rise. Water then flows from the tank through the gap between the two parts of the valve. When the level of water in the tank falls approximately to the level of the first part of the seal, the two parts of the valve seal against each other and as water continues to enter the tank the pressure difference across the seal holds the two parts of the seal in position and the seal is thereby restored. U.S. patent application Ser. No. 11/777,433 does not disclose how the float assembly shown in FIG. 4 of that application may be modified to achieve a dual volume flush, or how to adjust the volume of water that is discharged during a single flush.